Patent GB-759092-A (GB)
Title: A process for the manufacture of moulded articles of reinforced plastic material
IPC: B29C67/24
Filed: 1954-06-02
Abstract: A composition from which articles such as pipes and plates are moulded (see Group V) comprises liquid, unsaturated polyester resins with liquid polymerizable ethylene derivatives and catalysts, e.g. benzoyl peroxide, mixed with sufficient filling material, e.g. sand, broken stone, or fibrous material such as rope, glass, asbestos or synthetic materials to give a crumbly consistency.  On being tamped into a mould the composition solidifies, assisted if necessary by an elevated temperature.  The thixotropic effect of the tamping enables a high proportion of filler to be used, as in the following typical examples: (1) 100 parts polyester-styrol mixture, and 400-1000 parts granular quartz; (2) 90 parts polyester-styrol mixture, 10 parts styrol, and 1200 parts granular quartz; (3) 400 parts rope or glass fibre mesh coated with 100 parts polyesterstyrol mixture.  Other variations are obtained by combining compositions as in the above examples.  Colouring pigments may be added.ALSO:Articles such as pipes or plates are moulded by a process in which a liquid unsaturated polyester resin is mixed with liquid ethylene derivatives that cay be polymerized, with an organic peroxide catalyst, and with sufficient solid filling material to give a crumbly consistency, and the mixture is tamped by hand or machinery into moulds or formers. Hardening of the material may be assisted by heat.  The process may be modified by first subjecting the mixture of binding and filling materials to mechanical working, when the moulding may be performed without tamping, e.g. by extrusion or centrifugally.  The object is to increase the proportion of filling material to binding material without the mixture becoming insusceptible to moulding, and it is stated that, with tamping, articles may be produced which contain up to 15 parts by weight of filling material to 1 part by weight of binding material.  The polyester resin may be made by condensation of dibasic unsaturated organic acids with divalent unsaturated or saturated alcohols.  The ethylene derivatives may be methacrylic acid esters, vinyl acetate or stylrol and polymerized and hardened by the influence of a catalyst such as benzoyl peroxide.  Filling materials mentioned are river gravel, broken stone fragments, sand, asbestos fibre, cord and yarn. Colouring pigment may be added.  Rope or cord may first be coated with the binding material and then tamped into the mould, and uncoated cord or rope may be tamped in alternately with coated. The rope may be disposed so as to be tamped in a position in which it reinforces the corners and edges of the moulded article. The initial mechanical working may be done in the barrel of a screw extruder, after which the required section is obtained by extruding the mixture through a heated die.  Hollow articles lined with corrosion-resisting material may be moulded by first covering the core with a suitable thermoplastic material such as polyvinyl chloride or polyethylene, covering it with glass fibre or asbestos fibre mesh and then moulding the polyester composition as described, when the fibrous mesh binds the lining to the body. The mesh or web can be made to stick to the lining material by pressure or adhesive, or the two may first be formed together and then placed on the core. Corrosion-resistant coverings may be formed by an inverse process.